JPS60239437A - Production of trifluoroacetic acid and its chloride - Google Patents

Abstract

PURPOSE:The gas-phase reaction between CF3CHCl2, O2 and water is effected under such conditions as the feedstocks and the reaction products do not liquefy, using a completely mixing type reactor, as the feed stocks are continuously supplied and the products are continuously taken out, whereby the titled compound is obtained. CONSTITUTION:In the production of trifluoroacetic acid and its acid chloride by reaction between 1,1-dichloro-2,2,2-trifluoroethane, oxygen and water, their gas- phase reaction is effected under reaction conditions where the feed stocks and the products do not liquefy, using a completely mixing type reactor free from local heating, preferably an upright reactor provided with a stirrer and the starting materials are continuously fed and the products are continuously taken out to give trifluoroacetic acid and its acid chloride. The reaction temperature is preferably 260-320 deg.C and the pressure is 25-35kg/cm<2>. The oxygen is preferably fed 1-2mol per mol of CH2CHCl and water is 0.01-0.5mol.

Description

Detailed Description of the Invention The present invention involves continuously reacting 1,1-dichloro-2,2,2-trifluoroethane (hereinafter abbreviated as R-123), oxygen, and water to produce trifluoroacetic acid ( (hereinafter abbreviated as TFA) and trifluoroacetic acid chloride (hereinafter referred to as TFAC)
It is abbreviated as ).

TFAC is a compound useful as a raw material for producing agricultural medicines, and TFA is a compound useful as a raw material for producing agricultural medicines, as a reaction solvent, or as various catalysts such as esterification catalysts and condensation catalysts. Conventionally, methods for producing these compounds include the production of TFA by electrolytic fluorination of acetic acid fluoride (U.S. Pat. No. 4,022,8241);
1.1-) Method for producing TFAC by reaction of refluoro-2,2,2-trichloroethane and sulfur trioxide (Patent Application Publication No. 56-501Ei49) or 0.1
A method for producing TFAG (Japanese Patent Publication No. 58-2441f1) is known, in which R-123 containing less than % by weight of water is reacted with a hinge in the presence of active radiation and oxygen. However, in electrolytic fluorination, separation of the intermediate product trifluoroacetic acid fluoride and hydrogen is expensive, in the production method using mercury salts, the chemicals used are difficult to handle and are industrially disadvantageous, and in the method using active radiation, There are several drawbacks to the conventional method, such as the glass of the radiation source being devitrified by a small amount of hydrofluoric acid produced as a by-product, making it unusable for a long period of time. The applicant has already proposed a method that overcomes the drawbacks of these conventional methods. That is, R-1
In this method, TFA and TFAC are produced by thermally oxidizing 23 in the presence of water. (Japanese Unexamined Patent Publication No. 58-159440) The present invention relates to an improvement of the method already submitted by the applicant, and improves the reaction rate of R-123, TFA
The selectivity to TFAC and the reaction time are improved. That is, the present invention provides 1,1-dichloro-2,2
, 2-trifluoroethane, oxygen, and water to obtain trifluoroacetic acid and its acid chloride, under conditions in which the raw materials and the reaction product do not liquefy, and
The present invention relates to a method for producing trifluoroacetic acid and its acid chloride, which is characterized by carrying out a gas phase reaction while continuously supplying raw materials and removing reaction products using a complete mixing type reactor that does not cause local overheating.

The gas phase reaction with R-123, oxygen-1 and water is as follows.

2CF3 CHCl 2 + 02 + H20→CF
3COOH+ 0F3GOCI+ 3HCI In the gas phase oxidation reaction, the thermal decomposition reaction of R-123 and various side reactions accompanying this are likely to occur, and the generation of HF and the like is also considered. Furthermore, R-123, which is a reaction raw material, contains R-123a, which is an isomer of R-123 and is difficult to separate.
That is, CF2CICFHCI is mixed in during the manufacturing process of R7123, and in some cases, it may even be contained in amounts as high as 15 wt%. Therefore, hydrofluoric acid and hydrochloric acid are also generated by the oxidation reaction of R-, 123a as shown below.

2CF2CIcFHc l + 02→ CF2CIG
OCI+ CF2C1tl:OF +oF+H1ll:
1 On the other hand, R-123 (usually a trace amount of isomer R- as mentioned above)
(contains 123a), TFA and TF
When attempting to obtain AC, water acts as a catalyst, and it is known that the oxidation reaction of R-123 is difficult to occur in an anhydrous state. However, the presence of water increases the corrosion of the equipment due to the above-mentioned by-product hydrofluoric acid and hydrochloric acid. In particular, hydrofluoric acid is highly corrosive even in anhydrous form, and the glass used to cover the radiation source, as described in Japanese Patent Publication No. 5B-24418, cannot withstand long-term use. Although the publication teaches that glass or quartz light sources are damaged by hydrofluoric acid produced as a by-product in the liquid phase oxidation reaction of R-123, the present inventors have obtained the knowledge that the same is true in the gas phase oxidation reaction. ing.

As described above, in the crystallization reaction of R-123 in which water acts as a catalyst, it is industrially impossible to use active radiation, which requires a glass material that does not resist corrosion. Even in gas phase oxidation reactions where the amount of water present is limited to an extremely small amount, water may liquefy during the reaction process, and corrosion by hydrofluoric acid is unavoidable. In contrast, the method of the present invention does not require active radiation, and by using Hastelloy as the material for the entire reaction tank, the risk of corrosion can be prevented, and industrial operation for a long period of 9 days is possible. It is. Furthermore, since there is little risk of corrosion, there is no need to minimize the amount of water present, and the selectivity of TFA can be increased by adding water to the substrate necessary for catalytic action.

In the method of the present invention, the reaction is usually carried out under pressure at a high temperature of 200° C. or higher, and the reaction time is extremely fast, with a reaction tank residence time of less than 10 minutes. Therefore, in order to increase the reaction rate and suppress side reactions to increase the selectivity of TFA and TFAC,
It is important to mix the reactants uniformly and to equalize the temperature and concentration. The oxidation reaction of R-123 is an exothermic reaction using water as a catalyst. Therefore, local overheating occurs in the reaction tank, and side reactions such as thermal decomposition reactions are likely to occur.
This causes a decrease in the selectivity to A and TFAC and must be avoided. To prevent local overheating, a stirrer as shown in FIG. 1 is provided in the reaction tank, and in a vertical reactor as shown in FIG. 1 per minute in a 50mm reactor
By stirring at a speed of 00 rpm or more, preferably 150 rpm or more, heat can be effectively dispersed.

In order to maintain a uniform temperature level throughout the reaction tank, the first
A method such as providing a jacket as shown in FIG. 2 and exchanging heat with an external heat medium or between reaction raw materials and reaction products may be adopted. The reaction temperature in the gas phase continuous reaction of the present invention is 250 to 400°C, preferably 260 to 320°C, if a reaction pressure of 25 to 35 kg/cn is adopted.
selected from a range of If the temperature is lower than this, the reaction rate may decrease or the reaction may not occur, and if the temperature is higher than this, side reactions such as thermal decomposition reactions are likely to occur, which is not preferable.

In the method of the present invention, a complete mixing type reactor is used, and by completely mixing, temperature and concentration can be made uniform. To do this, in addition to the stirring operation and heat exchange operation described above, the reaction raw materials are supplied to the lower part of the vertical reaction tank as shown in Figure 1.
It is preferable to adopt a method in which the reaction product is taken out from the upper layer. Also, as shown in Figure 1, R-12
By setting the supply position in step 3 above the supply position of oxygen and water, the mixing of R-123 with oxygen and water becomes more uniform, which helps improve the reaction rate and selectivity of R-123. be. If the feedstocks are incompletely mixed, unreacted R-123 will accumulate, causing a large amount of oxidation reaction to occur at once, creating the risk of explosion. From this point of view as well, sufficient mixing is important. To prevent R-123 from becoming unreacted, R-123
The amount of oxygen supplied is preferably at least the theoretical amount, and from the perspective of explosion limits, is preferably about twice the mole or less. Therefore, the amount of oxygen supplied is selected from the range of 0.5 to 2 moles, preferably 1 to 2 moles, per mole of R-123.

゛The present inventors have discovered that when even a trace amount of reaction raw materials and reaction products liquefy in a reaction tank, droplets adhere to the wall of the reaction tank, and corrosive substances such as HCl and L(F), which are produced as by-products, are contained in the droplets. dissolved in
It has been found that this method corrodes the walls of the reactor, leading to undesirable results. As a result of corrosion of the reaction tank wall, metal chlorides are generated, and these chlorides act as negative catalysts and may even stop the oxidation reaction, and unreacted R-123 may oxidize at once, posing the risk of explosion. . R-123, a reaction raw material
The by-products HCl and HF are gases at room temperature, and although the reaction temperature of the present invention is high at around 300°C, there is a risk of liquefaction because the reaction pressure is high, about 20 to 40 kg/-. be. In particular, water that is liquid at room temperature tends to liquefy in the reaction tank, so it is necessary to avoid supplying more water than necessary.

In the oxidation reaction of R-123, water is thought to act as a catalyst and to hydrolyze trifluoroyl chloride produced by the oxidation of R-123 and convert it into trifluoroacetic acid. Therefore, it is preferable that the amount of water supplied is the minimum amount required for the catalyst, and at a level that does not liquefy and adhere to the walls of the reaction tank. Usually, it is preferable to select from the range of 0.01 to 0.5 mol per mol of R-1231. In order to prevent even the slightest amount of raw materials and reaction products in the reaction tank from liquefying, complete the oxidation reaction if the raw materials are raw materials and before the materials that have started to liquefy adhere to the walls of the reaction tank, and if they are reaction products, complete the oxidation reaction while stirring. It is important to disperse and extract the gas by entrained gas. Liquefaction of the raw material gas can be effectively prevented by preheating it to about 150 to 200°C before supplying it to the reaction tank. In addition, as for R-123, which is supplied in large quantities and is most likely to liquefy, as shown in Figure 1, it is supplied to the upper part of the reaction tank rather than water or oxygen.
Further, it is preferable to supply the mixture near the blades of the stirrer so that it is well dispersed and the oxidation reaction is completed.

The oxidation reaction of R-123 can be carried out in a completely mixed state as in the present invention, where the temperature and concentration are uniform. Just use it. The target compounds TFA and TFAC can be easily obtained by distilling the reaction product (shown in FIG. 1) taken out from the reaction tank. TFAC
is easily hydrolyzed to become TFA, but when it is desired to obtain only TFA, the reaction product 4 obtained by the present invention can be efficiently converted by adopting the two-stage hydrolysis step shown in Fig. 2. All can be TFA. The hydrolysis step shown in FIG. 2 will be explained below. The composition of reaction product 4 is mainly TFA, TFAC1 hydrochloric acid, and unreacted oxygen. The hydrolysis process shown in FIG.
1. First separation tank 12, conduit 16, first cooling tower 13. Conduit 18, second acetation tower 21, second separation tank 22, conduit 26,
It is discharged to the abatement system 29 via the second cooling tower 23. The TFAC to be hydrolyzed also passes through the same route as the hydrochloric acid and the like in a gaseous state, but by the time it passes through the second cooling tower 23, it has been completely hydrolyzed and converted into a TFA liquid. Water for hydrolysis is continuously supplied through the conduit 30 in an excess amount to the TFAG accompanying the hydrochloric acid, and is hydrolyzed in the second separation tank 22 and converted into a TFA liquid. This converted TF
Part A and unreacted water are circulated via conduits 24 and 25. The material that passes through the conduit 24 is introduced into the second cooling tower 23, and in the second separation tank 22, trace amounts of TFAC that are not hydrolyzed and may be accompanied by hydrochloric acid etc. are converted into TFA by water in the TFA liquid.
After being converted into , it is returned to the second separation tank 22 via the conduit 27. What passes through conduit 25 is introduced into second acetation column 21, where TFAC is hydrolyzed and returned to the second separation tank. By continuously performing such a circulation operation, the second separation tank 22 contains T containing about 5% by weight of water;
FA fluid accumulates.

The TFA liquid containing a small amount of water filled in the second separation tank 22 is intermittently transferred to the first separation tank 12.

The TFA liquid containing a trace amount of water in the first separation tank 12 is transferred to the conduit 1
4 and 15. The TFAC that passes through the conduit 14 is introduced into the first cooling tower 13, and the TFAC that is not hydrolyzed in the first acetation tower 11 or the first separation tank 12 and is accompanied by hydrochloric acid etc.
After being converted to TFA by the water in the FA liquid, it is returned to the first separation tank 12 via a conduit 17.

The material passing through the conduit 15 is introduced into the first acetation column 11, where TFAC in the reaction product 4 is hydrolyzed and transferred to the first separation tank 1.
Returned to 2. By continuously performing such a circulation operation, the amount of water in the first separation tank 12 is approximately 0.0.
TFA liquid having a concentration of around 1% by weight is accumulated. The TFAC that has undergone hydrolysis is transferred to the second acetation column 21 via conduit 18, and is finally completely converted into TFA by the excess amount of water that enters from conduit 30. After the TFA liquid containing about 0.01% by weight of water is transferred to the distillation process through the conduit 28, the TFA liquid containing about 5% by weight of water is transferred to the first separation tank 12. Water content inside is 0.0
The above-mentioned circulation operation may be repeated until the concentration becomes around 1% by weight. TF produced by the oxidation reaction of R-123
When converting all AC to TFA, such 2
A stage hydrolysis step is preferred. In other words, all of the TFAC can be converted and the water content in the target TFA can be reduced to 11%.
This is because it can be reduced to around 00pp.

When trying to convert all of TFAC to TFA, it is possible to add an excess amount of water and hydrolyze it all at once, but the resulting TFA may contain a large amount of unreacted water.
The separation operation requires a lot of effort. This is because TFA and water have an azeotropic composition, making it difficult to separate them by distillation.

Examples of the present invention will be described in more detail below.

Example 1 A vertical reaction tank as shown in FIG. 1 was equipped with a stirrer having two stages of upper and lower stirring blades as shown in FIG. 3 and a salmon throat type heat exchanger as shown in FIG. R-123, water, and oxygen were continuously supplied to carry out the reaction. R-1
The supply amount of No. 23 was set to 103n+ol/hr. R-12
The position of supply into the reaction tank in No. 3 was below the position from which the reaction product was taken out, and above the position where water and oxygen were supplied. These reaction raw materials were supplied near the lower stirring blade. Further, R-123 and water were preheated.

Reaction conditions, reaction rate of R-123, and TFA and TF
The selectivity of AC is shown in Table 1. The reaction rate and selectivity were determined by analyzing the reaction product by 19F-NMR and gas chromatography. The temperature difference in the reaction tank was determined by the temperature difference between the center of the upper stirring blade and the vicinity of the center of the lower stirring blade.

Table 1 Comparative Example 1 10.5 g (0.08 J
Mokuru) R-123 and 0.12 g (0,0011 mol) of water were charged, and the temperature was raised to 290°C. The pressure at that time is 1
5kg/co? Met. Add oxygen to it and it becomes 30 kg.
/cn and held for 5 minutes. After that, the contents were collected in a trap cooled with liquid nitrogen, and the trap was further immersed in a dry ice-ethanol bath to remove unreacted oxygen and generated hydrochloric acid, and the reaction liquid was analyzed by 19F-NMR and gas magnography. I did this. As a result, R-
Reaction rate of 123 52X, selectivity of TFA 22%, DingFA
The selectivity of C was 68%.

Comparative Example 2 The reaction was carried out in the same manner as in Comparative Example 1, except that the reaction rate of R-123 was increased and the holding time was changed to 8 minutes. As a result, the reaction rate of R-123 was 53z.

The selectivity of TFA was 20% and that of TFAC was 64%. That is, there was almost no change in the reaction rate, and on the contrary, a decrease in selectivity was observed.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing one embodiment of the gas phase reaction process of R-123, oxygen, and water. Figure 2 shows TFAC
Flow sheet showing one aspect of the hydrolysis process to obtain A. 1: Continuous vertical single tank reaction tank 11: First acetation tower 12: First separation tank 13: First cooling tower

Claims (1)

[Claims] A method for obtaining trifluoroacetic acid and its acid chloride by reacting 1, 1,1-dichloro-2,2,2-trifluoroethane, oxygen, and water, wherein the raw materials and the reaction product are liquefied. A method for producing trifluoroacetic acid and its acid chloride, which is characterized by carrying out a gas phase reaction while continuously supplying raw materials and taking out reaction products in a complete mixing type reactor that does not cause local heating and under conditions that do not cause local heating. . 2. The amount of oxygen supplied is 1,1-dichloro-2,2,2-)
The manufacturing method according to claim 1, wherein the amount is selected from the range of 1 to 2 mol per mol of refluoroethane. 3. The amount of water supplied is 1.0.0% per mole of 1-dichloro-2,2,2-)lifluoroethane The manufacturing method according to claim 1, wherein the amount of O is selected from the range of 1 to 0.5 mol. 4. The manufacturing method according to claim 1, wherein the reaction temperature is selected from the range of 260 to 320°C. 5. The production method according to claim 1, wherein the reaction pressure is selected from the range of 25 to 35 kg/cwt. 8. The manufacturing method according to claim 1, wherein the reaction is carried out after preheating 8,1,1-dichloro-2,2,2-h-trifluoroethane and water to 150 to 200°C. 7. The production method according to claim 1, wherein the complete mixing reactor is a vertical reactor equipped with a stirrer. 8. 1,1-dichloro-2,2, into a fully mixed reactor
2. The production method according to claim 1, wherein the 2-trifluoroethane supply position is below the reaction product take-off position and above the oxygen and water supply positions. ! 1. 1. The manufacturing method according to claim 7, wherein the supply position of 1-dichloro-2,2,2-trifluoroethane, oxygen, or water into the reactor is near the blades of a stirrer.